DHCP relay - N3024 stack

I have problem in which these N3024 L3 core switches (stacked) don’t perform dhcp relay.

Having inherited this little network and not worked on Dells for long, I thought I would post here in view you may be able to say if I am looking at a buggy IOS or a simple config mistake.

Setup inverted U design:

N3024 stack Dell N2048P stack Cisco 2960x stack

This issue only came to our attention when the cisco stack had a power failure and the site then started failing dhcp allocation, when the power was restored to that cisco stack dhcp stated to work again for the whole site

For me it It’s unusual having to apply relay on any access switch as naturally they are just host switches, and as it’s the L3 core( dell N300 in this case) where the L3 addresses for the vlans reside should where you need to be applying relay for the dhcp servers. However in this instance once the relay was removed from the 8th floor cisco stack everything fails on both floors which replicated the previous power issue to the cisco stack.

Wireshark capture with the failed tests confirms no dhcp offer ever occurring and on the success tests shows proxy to the cisco stack

L3 and 7th-8th access closets – success for both floors ( because its applied to cisco ) L3 and 8th- access closet – success for both floors ( because its applied to cisco )

8th- access closet only - – success for both floors

L3 core only – fails for both floors L3 and 7th- access closet – fails for both floors

7th access closets only - fails for both floors

I am fairly positive at this time it isn’t a configuration issue and tend to be thinking down the lines of a possible bug on the dell’s ios, but will need further investigation to confirm, hence this ticket to you guys.

I found a few older cases with similar DHCP issues. The two common fixes were a reboot, or firmware updates. If you are certain the config is good, I suggest looking at updating the firmware and testing again.

Daniel CoveyDellEMC | Enterprise Support ServicesGet support on Twitter:@DellCaresPRO

It curently set below on both the dell L3 and L2 stacksint vlan xxip helper-address x.x.x.x

The current config is just with the server address applied, however this has also been tested with the dhcp protocol, both together and with and without the global dhcp l2relay and ip helper enable command even though the latter this is supposed to be enabled by default - None have been successful.

Even tried with/without option 82 insertion, and with increased waiting times and nothing has worked

As I stated, I even captured the dhcp traffic and with all these various settings and it did even get past the discovery, but when applied to a Cisco L2 access stack everything kicked in and the DORA's initiated be it via proxying the cisco L2 switch stack

Do you have a related issue with this particular ios, I cannot seen to find any bug search tool like we have a cisco.

I found a few older cases with similar DHCP issues. The two common fixes were a reboot, or firmware updates. If you are certain the config is good, I suggest looking at updating the firmware and testing again.

Daniel CoveyDellEMC | Enterprise Support ServicesGet support on Twitter:@DellCaresPRO